Also, do I have to stop zimbra first by entering the following command zmcontrol stop, before starting the openldap command.
Again, I am not sure if I am using openldap, but I know that I am authenticating through my external ldap. In that case do I have to run the commands above. I thought the openldap is for the internal zimbra authentication.

What if I copy the entire zimbra directory to a remote location and restore back after setting up and configuring zimbra on my 64 bit machine, will that cause any trouble?

I am a bit confuse about the first step:

What does it do? Is it a single line command or 2 seperated commands

Also, do I have to stop zimbra first by entering the following command zmcontrol stop, before starting the openldap command.
Again, I am not sure if I am using openldap, but I know that I am authenticating through my external ldap. In that case do I have to run the commands above. I thought the openldap is for the internal zimbra authentication.

Please help me understand.

Thanks

No
it is one command for you since you are already in 6.0 it will be
6.0+: /opt/zimbra/libexec/zmslapcat /backup

Now I have migrated from 32 bit to 64 bit. I can telnet my email server, but I am unable to send email even within my domain neither am I able to receive. All mails coming in are being deferred. I am able to telnet my server from in and outside.
Please help